I know of an Archer which had a disproportionate IFR upgrade, including slaved HSI, and the little darling comes in at nearly 1800 lbs empty weight, which should be classified as more than a misdemeanour. In effect turning a practical tourer into an inefficient two seater. Another example is the lardy C182T which comes in at 2,100 lbs empty in some guises. Recall this was once a close to 10lbs/HP at gross weight machine, truly a four place Super Cub. Now a slow paced bovine.
In this spirit shouldn’t the new avionics be helping the original design return to its intended empty weight?
Some early Cessna 180 have pristine panels – no gyros except for an electronic turn coordinator, one com and Mode C. They boast sub 1,600 lbs empty weight.
With the G5 and the GI275 presumably one can design a minimalist airway kit that claims SRGY/LB2 on the flightplan form without adding too many pounds?
Maybe isolated examples? if you go glass you should shaft weight about 1lbs per 1k$ you put in
I know for Mooney: legacy AP is 30lbs, vaccum plus backup is 20lbs, that goes back as 20lbs in 2*G5 & GFC500, so you should get 30lbs if you put 30k$ 
RobertL18C wrote:
In this spirit shouldn’t the new avionics be helping the original design return to its intended empty weight?
If you replace steam by glass with same functionality it definitely should. In that sense a replacement for a full steam Sixpack would be a single G5.
Challenge is, that many glass upgrades don’t do like for like replacements but adding tons of features (that would add tremendous wheight if even possible when added in steam version) and therefore also add weight. In extreme: Two G500TXI are not at all lighter than a single traditional sixpack – but obviously so much more powerful…
Generally, G5 can indeed provide a full sixpack functionality, but the STC for it contains a few limitations:
(1) The installation of the G5 requires the retention of the mechanical airspeed indicator, altimeter, and vertical speed indicator.
(2) For installations in aircraft approved for IFR operations:
(a) If the G5 is installed as the primary attitude indicator, the existing rate of turn indicator must be retained.
(b) If the G5 is installed as the rate of turn indicator, the existing primary attitude indicator must be retained.
(3) For installations in aircraft approved for VFR-only operations, the G5 can be installed as the attitude indicator and rate of turn indicator without retention of either the existing attitude indicator or rate of turn indicator.
On the non-certified end, my Auster has two heavy World War II vintage gyros (a DG and a Sperry artificial horizon that’s so large there’s a special recess in the fuel tank so it’ll actually fit). A full non-certified modern IFR panel would weigh probably less than just one of those gyros (and the vacuum pump could be taken out). Also some of the engine instruments could be replaced by something new.
I have no intention of flying the Auster IFR, but even for day-VFR only, I’ve been mulling over redoing the panel (I would like a good engine monitor, and also I would like the opportunity to completely rewire the aircraft – it’s not complex wiring, and we did a tidy-up at permit renewal a couple of years ago, but there’s only so much you can do without stripping it all down and starting again). I’m sure we’d save several lbs.
Real cost of an avionics upgrade (in the DC area) :
EDM830 install : 5600$
GMA350 install : 3400$
Dual G5 install : 7900$
GTR225 install : 2200$
GFC500 install : 12000$
Pitot static check : 150$
He saved 60lbs (!!) in his IFR Archer.
He could remove his turn indicator. Maybe it is because of the second G5 ?
I can’t find it in the G5 install manual (as quoted above by ultranomad).
I removed my vacuum system, put in two g5’s and a gfc500 and saved 3lbs. so pulling a load of gyros and switching to g5’s should see some good weight savings
The GTR225 install seems pretty good value, it’s not much more than the purchase cost of the radio.
I hope I can add some data on dual g5 and trutrak install cost next week . My GTR225A and Trig-TT31 install were 800EUR each.
28hrs on gfc500. Thats fast. Ok aircraft was already open but anyway all this job at 100hrs is good.
